1. Field of the Invention
This invention relates generally to petroleum and natural gas and oil wells, and particularly to wellhead site equipment. More particularly, this invention relates to a sand separator installed at the wellhead upstream of other surface equipment for separating sand and rock debris from well effluent fluids.
2. Description of Related Art
Exploration for methane, or natural gas, involves injection of high-pressure fluids (mostly water with sand) directly into underground rock formations expected to yield natural gas, a process commonly referred to as “hydraulic fracturing.” The water pressure fractures the rock strata, whereupon entrapped natural gas escapes into the well bore to be captured at the surface and piped to market. Hydraulic fracturing fluid is recovered from the exploration wells and disposed of, usually by hauling it off in trucks to a remote disposal site.
Fracturing fluid contains a considerable amount of fracturing sand. The sand lodges in the cracks created by fracturing and holds open the cracks to maximize escape of natural gas from the strata. The sand also scours the formation to clean and etch it for maximum gas delivery. Sand included in fracturing fluid doesn't all lodge in the formation, however, and some returns to the surface in what is called the “flowback” from the well. During flowback, the well disgorges the fracturing fluid under pressure from the escaping natural gas. The flowback fracturing fluid includes a significant quantity of the injected sand, as well as granular rock debris flushed from the rock strata by the fracturing and flowback stages. Such sand and debris can wreak havoc upon choke valves that reduce the return fluid pressure and velocity downstream of the wellhead, and upon relatively sensitive surface testing, metering and processing equipment. A need exists for means for eliminating sand and rock debris from returned hydraulic fracturing fluid.
Production wells likewise need protection from fracturing sand and granular rock debris. Natural gas from producing wells comprises not only gaseous methane, but myriad other liquid byproducts, some of which are valuable (e.g. petroleum and natural gas distillates) and others of which are waste (e.g. stratigraphic saline and residual fracturing fluid), both of which may include significant quantities of sand. Surface equipment adapted for segregating well byproducts and for metering output from producing wells is vulnerable to damage from such debris. A need exists for means for separating solid materials such a sand and rock granules from producing well effluents.